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Full Idea
Lewis's argument for possible worlds parallels Quine's for the existence of sets: our best overall empirical theory, mathematical physics, quantifies over real numbers, so we have reason to posit real numbers, or the sets to which they may be reduced.
Gist of Idea
Lewis posits possible worlds just as Quine says that physics needs numbers and sets
Source
report of David Lewis (On the Plurality of Worlds [1986]) by Theodore Sider - Reductive Theories of Modality 3.6
Book Ref
'The Oxford Handbook of Metaphysics', ed/tr. Loux,M /Zimmerman,D [OUP 2005], p.194
A Reaction
They both strike me as suspect. Indeed, the extreme implausibility of Lewis's conclusion throws doubt on Quine's original strategy. I'm happy to work with sets and possible worlds, and only worry about ontological commitment at a later stage.
| 15472 | It is pointless to say possible worlds are truthmakers, and then deny that possible worlds exist [Martin,CB] |
| 5482 | Possible worlds realism is only needed to give truth conditions for modals and conditionals [Ellis] |
| 16959 | If possible worlds have no structure (S5) they are equal, and it is hard to deny them reality [Dummett] |
| 12255 | For Lewis there is no real possibility, since all possibilities are actual [Oderberg on Lewis] |
| 9219 | Lewis posits possible worlds just as Quine says that physics needs numbers and sets [Lewis, by Sider] |
| 15022 | If possible worlds really exist, then they are part of actuality [Sider on Lewis] |
| 10469 | A world is a maximal mereological sum of spatiotemporally interrelated things [Lewis] |
| 16283 | For me, all worlds are equal, with each being actual relative to itself [Lewis] |
| 12008 | Unlike places and times, we cannot separate possible worlds from what is true at them [Forbes,G] |
| 12009 | The problem with possible worlds realism is epistemological; we can't know properties of possible objects [Forbes,G] |
| 4586 | You can't embrace the formal apparatus of possible worlds, but reject the ontology [Heil] |
| 10982 | How can modal Platonists know the truth of a modal proposition? [Read] |
| 12465 | Concrete worlds, unlike fictions, at least offer evidence of how the actual world could be [Jacobs] |